Method of and apparatus for smelting tin.



G TIN.

Y' APPLICATION FILED NOV. 27. I9I I. 1271,2Q0

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Patented July 2, 1918.

2 SHEETS-SHEET I.

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Patented July 2,191.84

2 SHEETS-SHEET 2.

E. N. MORRILL.

APPLICATION FILED Nov. 21. I9I7.

METHOD 0F AND APPARATUS FOR SMELTING nztneoo.

,man srnfrns rA'EN'r onirica.;

EDMUND N. noname, or wennen, New Henneman, Assiette?. To Annes nxrtoar.vu 'rien a examine coaroaarion, .e coaroanrron or nnnawnan.

METHOD 0F All@ A'PPARATUS FR SMELTING TIN.

Specification of Letters Patent.

Patented July 2, MMS.,

vapplication nes-november er, ier?. serial no. aceite.

To all whom t may concern v i Be, it known that l, EDMUND N. Monnna., a citizenof the United States, residing at have invented certain new' and useful llmprovements in Methods of and Apparatus for Smelting Tin, of which the following is a clear, full, and exact description.

This invention relates to a process and apparatus for smelting tin ore electrically and the apparatus comprises an'- electric incandescent furnace of special lconstruction and although designed more particularly for the carrying out of the present process, yet its advantageous features may well be employed for other purposes.

in the smelting oftin ore, it is desirable tov prevent as far as possible, the vaporiza-V tion 'of' the reduced tin and, therefore, one of the ob]ects of this invention is to smelt the ore under a pressure and at a temperature which will minimize said vaporizationgf-@f course a very slight vaporization of tin will take place. from 'the molten tin metal but no great vaporizationi'will 'take place unless the tin reaches its boiling point, approximately` 10000 C. 'in the working of the present process, ll prefer to employ a jmolten slag bath as the resistant' between two separated electrodes in contact therewith to furnish the heat within the furnace necessary for smelting, forthe reason that byproper adjustment of thev distance between said electrodes and of the voltage of the electric current, the temperature-of the molten material in the furnace may be verycarefully regulated so asnot to exceed 16000' C.

rlhe Crucible Within the furnace is preferably kept closed against the admission of air and the pressure within said Crucible may be controlled by choking the discharge of gases through the exit due. The examination of the gases passingout of the exit ,Hue will be one way of determining, by the ab' sence or presence of the well recognized whitish smoke, whether the temperature in.

A the furnace is excessive.

ln carrying out the present process, l also prefer to employ a comparatively large current at low pressure. For example, the amperage may run from 1,000 to 2,200 amperes and the pressure of the, current is preferably from 20 to 110 volts. rihe depth of the slag bath and distance between the electrodes in contact therewith are suitably adjusted, so

New Hampshire,

' which vtin and introducing fresh charges, the pressure of the electric current must be capable of gradual adjustment through a wide range, andv this may be accomplished through any suitable system of voltage regulation.

A furthenobject of the present invention is to provide an electric furnace which will not leak tin and with Crucible walls of such refractory material as will not disintegrate under the destructive and decomposing tendencies of the molten slag and metal. As is well known, tin, lead and analogous metals are extremely penetrating when in a molten condition and it is a common experience with tin furnaces heretofore employed, that after being in use for some time, the walls become soaked with tin, and furthermore,'.

considerable ti'ii has been lost by its penetrat-l ing' through the walls and base of the furnace into theearth. lTo overcome this defect of prior flirnaces, the present furnace is built and supported upon a solid block or baseI of concrete with raised border walls which is practically 4impervious to the tin andserves as a collecting basin therefor.

.Furtherl`v objects and advantages of the presentzfprocess and apparatuswill become apparent in the following specification describes a suitable and preferred embodiment of the invention and the novel features thereof will be pointed out in7 the appending claims.

Referring to the drawings:

Figure 1 is a vertical section through the furnace along line 1-1 of Fig. 2.

Fi 2 is another vertical section through the furnace along line 2-2 of Fig). l; the sections shown in Figs. 1 kand 2 eing at right angles to one another.

ico

suitable fire brick. Within the walls 4 isinclosed the crucible 5, made of magnesite maintain the required pressure .erably four 1n number,

t ble and it is understood supported `by brick forming a lining therefor and topped overhead with a suitable arch, which may be of fire brick. The sides of the Aarches are beams of railroad iron 7, and I beams of railroad iron 8 are embedded in the concrete base 1, of the furnace extendingfore and aft therethrough, as shown so asto be tied to similar I beams 9, running over the top of the furnace. The I beams areconnected at their ends as shown in 2 by tie rods 10, having turn buckles l1 therein for taking up any looseness thereof as it occurs in th'e expansion and contrac- -tlon of the walls of the furnace. The fur- `nace. is also suitably tied together transversely by transverse rods12, embedded in the top and bottom of the furnace respectively, and with their protruding ends passing through vertical I beams 14, as shown 1n Fig. 1.

An eductor or flue for exhaust gases is shown lat 15, communicating with the top of the crucible and passing outwardly through the furnaceto the stack 16. A choke damper 17 is mounted in the eductor Hue 4s o as to chokethe dischar e of the exhaust gases therethrough an within the crucible. A plurality of feed holes 18, prefare provided through the arch of the crucible and top of the furnace, by which fresh charges of ore and material may be introduced into the crucithat normally, durlng the running 'of the furnace, Athe yfeed holes are closed by plug covers'19. The upperl electrode 20 of the furnace,

preferably a carbon stick, is shown as -en terlng centrally through the top of the crutcible and with at the bottom of A its lower end dipping slightly into the molten slag, the level of which is indlcated at 21.| .The floor of the crucible 5, 1s stepped downf to a central gutter 22, and the gutter 22, is exposed the 23. The lower electrode is of carbon and is carried a suitable conducting ele# lower electrode also p preferably upon the end of ment 24, embedded in the fire brick at the base of the furnace extendingV outwardly thereof for connection to an offset conductor 25. It will be-noted by referenceto Fig. 2 that said conductor 25 is offset upwardly wlthin the walls of the furnace and is ex' tended to the exterior of said wall fby arm 26,- Yat a'point abovefthe level 27a`of the molten metal within the crucible. iThe purpose of. this is to prevent theleakage of molten metal outwardly of said` furnace through the packed jointbetween said conluctor and the walls of the furnace.

The conducting arm 26 for to thereby' the .lower elemA upper support (not shown) to dip the elec-` the bath of slag v trode 20 more or less into 21, and likewise .the clamp 28 may be' loosened by bolts 29 for extending the' carbon stick 20 therethrough as the) same is consumed. t 30, 31 indicate the water circulation pipes for the water jacket of said clamp 28.

@A typical condition of the materials 'withinthe crucible-is illustrated more clearly in F ig. 3, wherein the. level of the molten l metal which gravitates to the bottom of the crucible is shown at 27 and the level of molten slag above the metal is shown at 21. Above the molten slag are separate heaps of a freshly introduced charge 18a and 18",

The

said vcharges being introduced through the feed holes 18. 'It is to be understood that When first introduced, the charge eyen /though containing some materials which might be heavier than the molten slag, nevertheless,

mixed with lighter elements, the charge as a whole or at least a substantial part of it will normally float on top ofv theslag bath until smelted down. Immediately, however, the heat ofthe slag bath' starts the chemical reactions whichtake place between the several elements of ducing the metal of the ore. In other words, the` metal of the ore is melted out of the chargeand gravitates through the slag 'bath to the level of the molten metal at the bottom of the crucible.

The magnesite walls of the crucible are the charge for re-- heating both of since these are thoroughly.

gradually fluxed and plates are shown at 40'. The t On a level with the bottom of the crucible f gutter is a tap hole 30 for the molten metal, Whlch opens into what is kuownas a cinder monkey 31, shown as comprising a wrought iron member with flaring mouth 32, and

water vjacketed walls 33. Pipes 34?, 35a are. l

the water circulation pipes for the water jacket 33 of said cinder monkey. A similar tap hole 34, is provided slightly above the Y oor of the crucible as shown in Fig. 1, for l i tapping out slag and a similar cinder @Onkey 35 is 'also provided for the slag tap hole and is likewise water jacketed at 36,v and provided with Water circulating pipes 37, 38. i

The furnace is rperated and the' present ln'ccess is preferably carried out as follows: Starting 'with the furnace cold, a small quantity of coke is introduced in the bottom of the Crucible around thc lower electrode and the upper electrode is lowered to come in contact with said coke., so as to give a closed circuit for the' electrical current through the coke to the lower electrode. The current is then sent through the electrodes at a pressure of about volts, the amperage at this time being rather high on account of the low resistance furnished by the coke. As the coke vbegins to glow red hot, easily fusible slag is introduced to furnish a slag bath within the crucible. The slag as it melts is slowly increased in depth by the introduction of new charges, and the upper electrode is gradually pulled away from the lower electrode untilv the resistance is increased sufliciently to cut down the amperage to about 1500 amperes. The molten bath of slag thus formed is preferably heated to a temperature'of about 1500o C., whereupon it is ready for the introduction of the ore to be smelted. The charge is then fed in small quantities through one or more ofthe feed holes described, the quantity of each charge thus introduced heing smaller than the volume of molten material already in the furnace so as not to perceptibly cool down saidy molten material. The charge vof ore and reducing materials is made up in approximately the following proportions:

60% concentrated tin Each charge upon coming in contact with the molten slag is heated sui'iciently to bring f about the chemical reactions necessary for reducing the tin ore, and the molten tin gradually sinks to the bottom of the crucible around the lower` electrode. The'lighter slag and other impurities rises and forms a bath above the molten metal.

During the working of the process, the voltage is regulated to maintain the required current for generating the necessary heat within the furnaceand is preferably maintained around 50 volts. Sometimes, however, it may be necessary to quickly raise the voltage as high as 110 or lower it to 20, in order to take care of special conditions. The molten metal is taped off at frequent intervals through the lower tap hole and cinder monkey 30, 31, and the slag is also tapped ofi' at suitable intervals through the upper tap hole 34 and 35. The upper carythe volume of said molten material approximately bon electrode 20, is adjusted up or down .whenprequired to keep its lower end just dipping within the slag bath and to main- 1-500 amper-es under a pressure of about 50 volts. During the running of the furnace a slight pressure is maintained within the same by choking the discharge of exhaust gases through the eductor 15, so that a temperature of 1500o C. within the furnace will quickly reduce the ore, without causing any appreciable vaporization of the molten metal.

It is to be understood, of course, that both the process heretofore particularly described and also the apparatus as shown and described-may be varied as to exact proportions or details of construction without departing from the spirit and scope of the invention as claimed.

VVhatll claim as new is 1. The process of smelting tin ore in an electric incandescent furnace, which consistsin forming a/ molten slag bath in said furnace by its resistance to an electric current passing therethrough, introducing at intervals into said bath, a charge of tin ore, slag and reducing materials, each freshly introduced charge being smaller in quantity than already in said furnace, and maintaining the telnperature of said bath approximately uniform and slightly below the boiling point of tin. I, Y

2. The process of smelting tin 'ore in an electric incandescent furnace, which consists in forming a molten slag bath in a `furnace closed to the atmosphere by its resistance' to an electric current passing therethrough, in-` troducing at intervals into said bath, a I

charge of tin ore, -slag and reducing materials, each freshly introduced charge being smaller in quantity than the volume of said molten material already in said furnace, and maintaining the temperature of said bath uniform and slightly below the boiling point of tin.

3. The process of smelting tin ore in an electr-ic incandescent furnace, which consists in forming a molten slag bath in said fur-` nace by its resistance to an electric current passing therethrough, introducing at intervals into said bath, a charge of tin ore, slag and reducing materials, each freshly introduced charge being` smaller in quantity than the volume of said molten' material already inl said furnace, and maintaining the temperature of said bath approximately uniform and slightly below the boiling point of tin and choking the discharge of gases from said furnace to retard the'vaporization of said tin.

4. The process of smelting tin ore in an electric incandescent furnace; which consists in forming a molten slag bath in said furnace by its resistance to an electric current 4 maintaining the temperature ofsaid 'bath and reducing materials,

duced charge being smaller in quantity thanf Y the molten and maintaining the temperature@ taining moltenmaterial andlined with reslightly vss , I prising brick, vsaid lining being approximately uniform and slightly below the boiling point of tin.

5. The process of lslnelting tin' ore in an electric incandescent furnace, which-consists in forming a molten slag bath in said furnace by its resistance to Van electric current passing therethrough, introducing at intervals into said bath, a charge of tin ore,y slag each freshly intrometal material already in said furnace, of said bath approximately uniform and below the boiling point of tin by a current varying from 1500 to 2200 amperes and under pressures of from 35 to60 volts.

6. The process of smelting tin ore'in an electric incandescent furnace, which consists in forming a molten slag bath in said furnace by its resistance to an electric current lpassing therethrough between separated electrodes in contact with said bath, introducing at intervals-intosaid bath, a charge offore, slag and reducing materials, each freshly introduced charge being smaller in 'quantity than the material already in said furnace, maintaining'the temperature of said bath approximately uniform and slightly below the boiling pointv of tin and ltapping olf said slag and said' reduced metal at intervals but never inV greater quantit than that which will dy keep the electrodes ipping in said bath. A

7. An electric incandescent furnace com- .a crucible llined with magnesite surrounded by a backing of fire-brick and the wholesupported upon a solid base of concrete having a raised border wall to prevent leakage of ported upon a solid base of concretelhaving a raised border wall to prevent leakage of molten material from said furnace into the earth, the hearth of said crucible being surrounded by water-cooled plates located adjacent said magnesite lining,"tap holes for said slag ferent levels, each of said tap holes having outwardly flaring mouths and being sur# rounded with a water jacket.

' 9. A11 electric incandescent furnace closed on all sides, comprising acruc'ible for conmaterial and having supporting fractory an upper electrode projecting through walls,

and for said molten metal at difi the top of. sald furnace and a lower electrode .x

at the bottom of said crucible, fsaid lower electrode entering the side wall of said fur.

"nace at a point above the level/of molten material within said crucible and bein olf- 4set downwardl within said side wa to project into t thereof. A f- .10. An electric incandescent furnace, comprising a crucible for containing molten material and having upper and lower electrodes, the lower velectrode bein through the bottom of said crucib e trical contact with being ofi-'set laterallyzv and upwardly within the wall of said crucible so as to extend outwardly through the said wall thereof at a point above the level of the molten material 1n.said crucible. Signed at New York, N. Y., this 15th day -of November, 1917. v l

for elecexposed e crucible at the bottom said molten material and 

